Labdb: debug logging — register payload + HTTP 응답 body 출력

INTERNAL_ERROR(500) 원인 좁히기 위해 LabdbClient에 logcat 추가:
- POST /devices/register 보내는 정확한 payload (TAG=LabdbClient)
- 모든 응답의 HTTP code + raw body (앞 500자)
- IOException 발생 시 스택 trace

logcat 필터: tag:LabdbClient

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/src/main/java/com/example/medilightv2android/services/labdb/LabdbClient.kt

@@ -2,6 +2,7 @@ package com.example.medilightv2android.services.labdb
 
 import android.content.Context
 import android.os.Build
+import android.util.Log
 import com.example.medilightv2android.ble.BleManager
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
@@ -43,6 +44,7 @@ data class UploadResult(
  * 모든 메서드는 suspend, IO 디스패처에서 실행.
  */
 object LabdbClient {
+    private const val TAG = "LabdbClient"
     private const val BASE = "https://labdb.medithings.net/api/v1"
     private const val APP_NAME = "VesiScan"
     private val JSON = "application/json; charset=utf-8".toMediaType()
@@ -66,6 +68,7 @@ object LabdbClient {
             ble.serialNumber.value.takeIf { it.isNotEmpty() }?.let { put("serialNumber", it) }
             put("appVersion", appVersion)
         }
+        Log.d(TAG, ">> POST /devices/register payload=$body")
         val req = Request.Builder()
             .url("$BASE/devices/register")
             .post(body.toString().toRequestBody(JSON))
@@ -157,10 +160,12 @@ object LabdbClient {
         return try {
             client.newCall(req).execute().use { res ->
                 val raw = res.body?.string().orEmpty()
+                Log.d(TAG, "<< ${req.method} ${req.url.encodedPath} → HTTP ${res.code} body=${raw.take(500)}")
                 val obj = if (raw.isBlank()) JSONObject() else runCatching { JSONObject(raw) }.getOrElse { JSONObject() }
                 res.code to obj
             }
         } catch (t: IOException) {
+            Log.w(TAG, "exec failed: ${req.method} ${req.url}", t)
             throw LabdbNetworkError(t)
         }
     }